Was Sabbath lost because of a calendar change?
Our calendar has been changed once since the time of Christ. In 1582, the Gregorian calendar displaced the Julian calendar but, while the dates of the month were changed on the calendar, the days of the week and their sequence were not altered in any way. Jesus, who created the week as well as the Sabbath in the beginning, would have known of any error in the weekly cycle and would surely have corrected the error if the Sabbath would have been on the wrong day in His lifetime.
No calendar errors
However, there was no error, for the Sabbath that was observed immediately following Jesus’ death was the true Sabbath "according to the commandment”, and His disciples kept the seventh day faithfully as the Sabbath. The weekly cycle in the Jewish calendar has not been changed through the centuries, yet it agrees perfectly with our Roman calendar as far as the weekly cycle is concerned.
No time lost
By mathematical calculations, modern astronomy is able to reckon time forward or backward, and the loss of even one minute can be promptly detected. Read the testimony of these noted astronomers:
"The week of seven days has been in use ever since the days of the Mosaic dispensation, and we have no reason for supposing that any irregularities have existed in the succession of weeks and their days from that time to the present.” Dr. W. W. Campbell, Director of Lick Observatory, Mt. Hamilton, California.
"For more than 3,000 years science has gone backward, and with profound research, reveals the fact that in that vast period the length of the day has not changed by the hundredth part of a single second of time." Gen. O. M. Mitchell, Astronomy of the Bible, p. 235.
Compare the sources
Not many years ago, suppose that you wanted to set your watch correctly. You would pass three watchmakers' shops, and, if their official clocks gave the same hour and minute, you would be satisfied as you have obtained the correct time.
In the same way, if you want to know if your calendar is right, just check it by the calendars of the Jews, Muslims and pagans. What will you find? Perfect agreement--Sunday the first day of the week, and Saturday the seventh. The Jewish calendar stands unchanged through the centuries as does the Muslim calendar. Any change of the weekly cycle would readily be discovered by such a comparison.